Clarification is being sought of the relationship between experimental diabetes mellitus in the rat (streptozotocin, 80 mg. per kilo) and the net biosynthesis of plasma glycoproteins by the isolated perfused liver from these rats at 2 to 52 weeks after the onset of diabetes. Measurements with specific antisera by single radial or electroimmunodiffusion of albumin, fibrinogen, alpha1-macroglobulin, alpha2-macroglobulin and haptoglobin are being made to evaluate the effects of insulin treatment on net biosynthesis of these proteins. Possible correlations between diabetes mellitus, plasma glycoproteins and renal glomerular morphology will be looked for.